The ease with which a tire becomes unseated (that is to say with which the bead of the tire leaves its seat) and then comes off the rim (becomes detached from the rim) when its inflation pressure decreases and when a transverse load is applied to the tire is one of the tire features that is important for the safety of the passengers of a vehicle equipped with tires. The standardization authorities have thus set target values to be achieved (as for example in Chinese standard GB/T 2978-2008) and corresponding test methods (for example the method recommended in Chinese standard GB/T 4502-2009). An example of a test method is also described in the U.S. Pat. No. 3,662,597, according to which a conical form is applied against a sidewall of the tire and then the pressure exerted on the sidewall is increased and the movement of the sidewall is recorded. A similar test method has been adopted in “Federal Motor Vehicle Safety Standard No. 109” by the NHTSA (National Highway Traffic Safety Administration), the American federal road safety organization.
Among the envisaged solutions, the resistance to unseating could be increased by bonding the tire to the mounting rim, but this solution has the drawback of making it very difficult to remove the tire. It would also be possible to modify the geometry of the rim in order to make unseating more difficult, but this approach would require destandardization.
The document GB 2 085 375 A discloses an adapter that can be disposed between each tire bead and each rim flange. Each adapter comprises an axially outer end and an axially inner end that each have a reinforcer. Each reinforcer is surrounded by a single ply (elastomeric material/textile reinforcer). This ply connects each of the ends to one another.
The document DE 25 14 883 A1 describes a mounted assembly comprising a tire, a rim and at least one adapter. This adapter also comprises an axially outer end and an axially inner end that each comprise a reinforcer. Each end comprises a stop ring having reinforcing inserts made up of textile or metal threads. Moreover, the adapter of that document rests entirely on the rim.
However, such adapters also comprise complex constituents of the reinforcement ply type comprising an elastomeric composition and textile reinforcers, as connecting elements, and do not allow a mounted assembly to radially deform correctly.